Spindle-shaped supersonic projectile with additional propulsion by sternfiring



Dec. 8, 197 0 e. LUDWIG 3,545,212 SPINDLESHAPED SUPERSONIC PROJECTILEWITH ADDITIONAL PROPULSION BY STERN-FIRING Filed Dec. 14, 1967 V W, 4%MA.

' ,drrok/vers United States Patent Office 3,545,212 SPINDLE-SHAPEDSUPERSONIC PROJECTILE WITH ADDITIONAL PROPULSION BY STERN- FIRINGGiinter Ludwig, Kiel, Germany, assignor to Dynamit NobelAktiengesellschaft, Troisdorf, Bezirk Cologne, Germany Filed Dec. 14,1967, Ser. No. 690,539 Claims priority, application Switzerland, Dec.16, 1966, 18,132/ 66 Int. Cl. F02k 7/10 US. Cl. 60-270 1 Claim ABSTRACTOF THE DISCLOSURE A supersonic projectile capable of driving throughexternal combustion along its aft surfaces comprising a spindle-shapedbody having a forward section, an aft section, and a conical enlargementsection located between the forward and aft sections, each of theforward and aft sections being defined by the revolution of a slightlycurved line segment so as to present both a pointed forward end and apointed aft end and ends of greatest diameter for each of the forwardand aft sections. Fuel exit openings are provided at the largest end ofthe forward section immediately upstream from the conical enlargementsection whereby, in addition to the compression shock emanating from thepointed forward end, a second, weaker oblique shock-wave is produced byreason of the conical enlargement section.

Supersonic projectiles have been known which have a spindle-shaped bodypointed in the front and rear and which, by combustion of a sufficientlyrapidly burning fuel in the area of the largest diameter of theprojectile, will receive an additional drive. The largest diameter ofthe projectile will therefore be located at the contact area of linesextending parallel to the longitudinal axis of said projectile. In thecase of this additional drive known as a tail heating or externalcombustion, the difficulty is in the ignition of the fuel. Customarily,a liquid, a liqiud gas or a highly compressed gas is used as a fuelwhich emerges from openings distributed along the periphery on or behindthe largest diameter of the spindle-shaped body and which burns with theaid of the oxygen of the air. Such a tail heating or external combustionwill be come effective and economical only when the relative speedbetween the air and the supersonic projectile amounts to at least 3Mach. The fuel ignition speed therefore must be correspondingly high sothat the flame will not be broken in the supersonic current. There arefuels which will fulfill this condition, for example, aluminumborohydride. Such fuels, however, are spontaneously flammable in air andtherefore their handling and technical exploitation is difficult. Ahousing in, for example, projectiles that are to be fired from a tube,does not seem to be realizable as yet for the time being. In the case ofsupersonic projectiles, the so-called wave resistance will occur inaddition to the resistances brought about behind the projectile byfriction at the surface of the projectile and the formation of eddies,which wave resistance is brought about through the system ofcondensation as a result of compression shocks and expansion wavesdeveloping around the flying body. In the compression shocks, thedensity of the surrounding air changes irregularly while it steadilydecreases in the diverging fields of expansion waves. The impulsedelivered to the surrounding air for the change in density correspondsto the wave resistance. In order to keep these losses as small aspossible, it has been known to develop supersonic projectiles, so calledminimum bodies. These 3,545,212 Patented Dec. 8, 1970 have a minimumwave resistance since the diverging expansion waves will reduce asstrongly as possible the compression shocks on the basis of acorresponding profile shape, by interference with an increasing lateraldistance from the body of the projectile, and will counteract in thismanner, an expansion of the wave emanating from the projectile.

The inventtion will make even slowly igniting and less dangerous fuelsburn continuously in the supersonic stream with technical means on thebody of the projectile and will thus make them usable for the additionaldrive of supersonic projectiles.

The invention relates to a spindle-shaped supersonic projectile capableof drive through tail heating or external combustion along its aftsurfaces, with a front part of the projectile converging into a pointedforward end a rear part of the projectile tapering afterwards, a conicalenlargement between said forward and rear parts, and fuel exit openingsat the enlargement which comprises the largest diameter of theprojectile. This conical enlargement in addition to the compressionshock emanating from the pointed forward end of the projectile, producesa second, weaker oblique shock-wave in the area of the fuel exitopenings, which on the basis of the compression taking place during thistime and on the basis of the increase in the temperature of the air,will maintain in an effective manner the combustion of the customaryfuels, for example, hydrogen, in the case of a supersonic stream. Themagnitude of this second compression shock at the same time is dependenton the angle and the diameter of the conic enlargement.

In a practical development of the invention provision has been madeaccording to the invention to continue the contour of the tail of theprojectile without interruption downstream from the outside edge of theconical enlargement. For this purpose, the tail end of the projectilecan be developed for example in a known manner likewise as a minimumbody. However, in view of the effect intended with the drive, it will bemore advantageous if according to a further proposal of the inventionthe contour of the tail part of the projectile tapers toward the end ofthe projectile in such a manner as the volume of combustion gasesincreases in consequence of the continuing combustion of the fuel towardthe end of the projectile and expansion of the combustion gases, so thatthe cross sectional size of the space occupied by the tail end of theprojectile and the production gases will come as close as possible tothe largest cross section of the projectile beyond the longitudinalextent of the tail end of the projectile. Such a development willguarantee optimum conditions concerning an additional acceleration andstabilization of the projectile since the combustion gases are, so tospeak, in the shadow of the projectile and consequently will beinfluenced to a minimum measure by the surrounding air, so that thepressure forces exerted by the combustion gases on the tail end of theprojectile, the axial component of which causes the acceleration and theradial component of which causes the stabilization of the projectile,will reach their greatest possible value.

Further objects will be apparent from the following descriptionwhenconsidered in connection with the accompanying drawing which is across-section of the projectile. The supersonic projectile shown inlongitudinal section has a spindle-shaped body which is pointed fore andaft. It has been developed as a forward section 10 in its front part andit produces the compression shock 1 with its point. In the area of thelargest diameter of the forward section fuel exit openings 2 areprovided and are divided evenly over the periphery. The area of largestdiameter is where tangent lines on the projectile run at leastapproximately parallel to the axis of the projectile.

Downstream from the exit opening 2, the projectile has the conicalenlargement 3, which produces a smaller second compression shock 4. Thetail end or aft section of the projectile coverages directly from theoutside edge of the conical enlargement 3 and is developed by therevolution of a slightly curved line segment similar to the forwardsection of the projectile. Also, the tail part of the projectile may becontinued in such a manner to the combustion process that optimumconditions will be achieved with regard to the thrust and stabilizationof the projectile.

The direction and size of the curvature of the after section 5 contourwill be selected such that the crosssectional size of the space occupiedby the aft section of the projectile and the combustion gases will comeas close as possible to the largest cross-section of the projectile viathe longitudinal extent of the aft section of said projectile.Accordingly, in the case of a quickly burning fuel, the tail part of theprojectile will have to taper even more strongly directly behind theconical enlargement 3 than in the case of a slowly burning fuel.

The conical enlargement 3 may be adapted easily to the pertinent needsthrough a corresponding dimensioning of the angle and of the outsidediameter in order to produce a second compression shock 4 which willsuflice for the permanent ignition of the pertinent fuel, which shockwill not bring about more resistance than is absolutely necessary. Forexample, with a conical surface of 28 degrees in the case of an air flowof 3 Mach, hydrogen can be brought to continuous combustion.

I claim:

1. A supersonic projectile capable of drive through external combustionalong its aft surfaces, comprising: a spindle-shaped body having aforward section; and aft section; and a conical enlargement sectionlocated between said forward and aft sections; said forward sectionbeing defined by the revolution of a slightly curved first line segmentso as to present a pointed forward end and an end of largest diameterfor said forward section downstream of said pointed forward end; fuelexit openings provided along said largest diameter end; said conicalenlargement section being defined by a conical segment divergingdownstream directly from said exit openings, the divergent end of saidconical segment defining the outermost protrusion on said body; and saidaft section, which is defined by the revolution of a slightly curvedsecond line segment so as to present a pointed aft end, convergingdownstream from said divergent end of said conical segment to saidpointed aft end whereby, in addition to the compression shock emanatingfrom said pointed forward end, a second, weaker oblique shock-wave isproduced by reason of said conical enlargement section.

References Cited UNITED STATES PATENTS 3,008,669 11/1961 Tanczos -2703,074,668 1/ 1963 Frenzl 60-270 3,363,421 1/ 1968 Ferri 60-270 DOUGLASHART, Primary Examiner

